The research proposed here represents a union of cognitive psychology and speech/ hearing science. Cognitive theory and methods will be used to test the hypothesis that speech perception requires significantly more cognitive effort--i.e. ATTENTION-for hearing-impaired listeners than it does for normal-hearing listeners. The increased effort is needed to compensate for hearing-impaired listeners' sensitivity deficits, which limit their perceptual access to phonetic cue redundancies in speech. Given the finite nature of the human attentional capacity, we expect that if hearing-impaired listeners are indeed devoting exceptional attention to speech processing, then they should experience special difficulty in perceiving speech and performing concurrent cognitive activities. Specifically, we expect that (1) hearing-impaired listeners should suffer a significantly greater loss of speech understanding than normal-hearing listeners when attention is demanded by concurrent activities, and (2) hearing-impaired listeners' performance on concurrent activities should suffer disproportionately when they must focus their attention on speech understanding. Four experiments will address the issue of how performance of a speech perception task interacts with performance of a concurrent perceptual/cognitive activity for normal-hearing subjects and for hearing-impaired subjects with varying degrees of residual hearing. The first two experiments will employ a concurrent short-term memory task, the third a concurrent spatial hearing task, and the fourth will manipulate cognitive load by varying speech stimulus target set size. This investigation, like recent studies of listening to speech under reverberant and/or noisy conditions, is intended to provide a more comprehensive picture of hearing-impaired individuals' speech understanding as it takes place in everyday communication situations. Our particular interest is in the everyday requirement that a listener not only perceive speech but, at the same time, carry on other cognitively demanding activities such as taking lecture notes or driving a car. We expect that our findings regarding speech understanding in cognitively demanding circumstances will have relevance for the design and evaluation of sensory aids, and for the education of children with hearing impairments.